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this paper, ballistic impact on sandwich panel with composite facesheet made of Glass/Epoxy and aluminum honeycomb core has been investigated experimentally. Ballistic impact test also carried out on Honeycomb and composite and the effect absorption energy by adding composite on two sides honeycomb is studied. By this model the influence of the components on the behavior of the sandwich panel under impact load was evaluated. Ballistic impact tests is carried out on the samples by flat-ended projectile with 8/5 gr mass and 10 mm diameter in difference velocities. Also, the contribution of the failure mechanisms to the energy absorption of the projectile kinetic energy was determined. The results show that honeycomb sandwich has more energy than when alone ballistic tests conducted on has absorbed and front cover compared with back cover sandwich structure has lower energy absorption. Also bigger than ballistic limit velocity absorbed the maximum amount of energy.

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In this paper, ballistic impact on sandwich panel with composite face sheet made of Glass/Epoxy and aluminum honeycomb core has been studied. The solution is derived from a wave propagation model. At first both analytical and numerical solutions were clarified and their results were compared with experimental results. Some deformation patterns, failure modes and energy absorption mechanisms were identified by observation, such as: dynamic movement of the target, stretching, bending deformation, delamination, debonding, shear fracture honeycomb, tensile fracture of Glass/Epoxy and plug and petal formation in composite facings. The solution involves a four-stage and effective masses of the face sheets and core as the shock waves travel through sandwich panel are derived using Lagrangian mechanics. The resulting non-linear differential equation of motion was solved considering the local damage effects and corresponding energy absorptions. Also numerical model, analysis of the penetration process was performed by a nonlinear explicit finite element code, LSDYNA. The results of analytical solution and numerical simulation are compared with experimental tests. Ballistic impact tests is carried out on the samples by flat-ended projectile with 8/5 gr mass and 10 mm diameter in difference velocities.

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Thin-walled structures are frequently used as energy absorbers in automotive, railway and aviation industries. This paper deals with the collapse and energy absorption behavior of thin-walled structures under dynamic axial loading Numerical modeling was performed using finite element code LS-DYNA. In order to validate the results of finite element analyses, a square tube was collapsed using universal test machine. This tube was then simulated in LS-DYNA, and the results with those of experiments were compared. There was a good consistency between the numerical and experimental results. The tubes with different cross-sections namely square, hexagonal and octagonal shapes reinforced with inside ribs as well as with different scales (ratio of sectional side length of the inner tube to that of outer tube) 0, 0.25, 0.5, 0.75 and 1 were simulated in LS-DYNA. To determine the suitable cross-section in terms of crashworthiness, multi-criteria decision making method known as Technique of Order Preference by Similarity to Ideal Solution (TOPSIS) was employed. The results demonstrated that the double walled tube with octagonal cross-section possessing the scale between 0.25 and 0.5 had the best crashworthiness behavior. To find the optimum values of scale and wall-thickness, response surface method (RSM) and D-optimal criterion using design of experiments (DOE) were utilized Moreover, the effect of number of inside ribs (4 and 8) on the capability of absorbing energy was also investigated and the octagonal tube with 4 inside ribs was selected as an optimal tube with lower maximum impact force.